Find the value for the discriminant for the following equation: (2x +1)(x – 3) = 0

Question

zepdrix · Answer

Hey Jacky :)
Do you understand how to multiply out the bracketed terms?

zepdrix · Answer

We need this in standard form before we can look at the discriminant:
$\Large\rm ax^2+bx+c=0$

anonymous · Answer

Yes. I do. I would get 2x^2-5x-3

zepdrix · Answer

Mmm ok great!

anonymous · Answer

I am confused on what I should do next.

zepdrix · Answer

Our quadratic formula allows us to solve for x,
$$\Large\rm x=\frac{-b\pm\sqrt{\color{orangered}{b^2-4ac}}}{2a}$$

The discriminant is the orange part, that's all we're concerned with here.

anonymous · Answer

I got 7, is that correct?

zepdrix · Answer

$$\Large\rm \color{orangered}{b^2-4ac}$$Usually we want to know if this `greater than` `equal to` or `less than` zero,
to find out information about the polynomials roots.

zepdrix · Answer

$$\Large\rm \color{orangered}{b^2-4ac}=(-5)^2-4(2)(-3)$$

zepdrix · Answer

Hmm 7 doesn't look quite right :o

anonymous · Answer

so would it  be 49? I do not square root the b^2-4ac part?

zepdrix · Answer

Correct :) No square root needed.
They just want the `value` of the discriminant (stuff under the root).

Yay good job \c:/

anonymous · Answer

Alright, thanks! I understand now. :)

zepdrix · Answer

cool